realtek: use devm_kzalloc() for serdes debugfs setup
This will free memory automatically during driver unloading.
Signed-off-by: Markus Stockhausen <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/21157
Signed-off-by: Robert Marko <[email protected]>
(cherry picked from commit a4011797c2fb160a696edfc29993c78ab5edc3d1)